A quiet supersonic aircraft is a supersonic aircraft that will be able to comply with applicable governmental restrictions on the magnitude of sonic booms for flight over land or over other restricted areas, when such restrictions are set. Quiet supersonic aircraft will be designed to comply with such governmental restrictions when flying at a predetermined supersonic speed (e.g., Mach 1.7) and at predetermined atmospheric conditions (e.g., standard atmospheric conditions) and at predetermined operating conditions (e.g., throttle settings, angle of attack). When flying at the predetermined speed and the predetermined operating conditions through the predetermined atmospheric conditions, a quiet supersonic aircraft will have a pressure field around the aircraft that is substantially free from steep pressure gradients. As used herein, the phrase “steep pressure gradient” refers to a relatively large change in pressure over a relatively short distance.
A pressure field free of steep pressure gradients, when propagated to the ground, can give rise to a sonic boom having a magnitude that falls below governmentally imposed limits. Any deviation from the predetermined supersonic speed or from the predetermined atmospheric conditions or from the predetermined operating conditions may give rise to a steep pressure gradient in the pressure field. If a steep pressure gradient were to form in the pressure field around the aircraft during supersonic flight, this could have an undesirable effect on the magnitude of the sonic boom that propagates to the ground.
The propulsion system of a supersonic aircraft interacts aerodynamically with the airframe and with the pressure field around the supersonic aircraft. For example, the flow of air ingested by the propulsion system's inlet, the cycle at which the propulsion system's engine is operated, or the exhaust plume expelled by the propulsion system's nozzle will interact with the airflow around the supersonic aircraft's airframe. A quiet supersonic aircraft is designed such that when the propulsion system is operating at its design condition, the effect of the propulsion system on the pressure field will not give rise to a relatively steep gradient in the pressure field. As used herein, a reference to the design condition of a propulsion system refers to the predetermined engine cycle, the predetermined Mach speed, the predetermined atmospheric conditions, and the predetermined throttle settings that the engine will be operating at when the aircraft is operating at its design condition.
However, when operation of the propulsion system deviates from the design condition (e.g., throttle settings that deviate from design throttle settings, operation at speeds other than design Mach speed, operation of the engine at an engine cycle that differs from a design engine cycle, operation of the propulsion system in other than the predetermined atmospheric conditions, etc.), the propulsion system can cause a relatively steep gradient to form in the pressure field around the aircraft. This is undesirable.
Accordingly, it is desirable to provide a system that can control the pressure field around an aircraft in flight. In addition, it is desirable to provide a method for controlling the pressure field around an aircraft in flight. Furthermore, other desirable features and characteristics will become apparent from the subsequent summary and detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.